4WD No Good - Mystery Knock/Slap/Vibration

Goldbug

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I'm trying to make sure my 40 is ready for the Fall Gathering event in NH in a week, and put it in 4High for the first time in a while. I got a pretty intense sound coming from the front of the vehicle. Sounds like driveshaft is loose. But it's not. It happens in 4H, going above 20MPH or so, most noticeable when coasting vs accelerating. When driving, doesn't matter if hubs are locked or not.

I put it on jack stands, removed the rear driveshaft and "drove" it in the garage last night. Sound is not as loud (less load?), and is significantly worse with hubs locked. I took a video, apologies for the belt whine, I need to shim out the aftermarket PS that the PO installed. You can hear the rattle/slap sound starting about 8 seconds in.

Any ideas? I'm thinking hubs or front diff. I've driven the heck out of it lately in 2H with no issues.
 

Shark56

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Any chance your front drive shaft is hitting on the skid plate?
 

Goldbug

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Any chance your front drive shaft is hitting on the skid plate?
I wish I had a skid plate!

With it up on the jack stands, trying to rock the wheels top to bottom, the drivers side is rock solid. The passengers side has a wiggle, which suggests I installed the new wheel bearings incorrectly in the spring. I wouldn't think that could do all of this though? Maybe knuckles?
 

Goldbug

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I may just go with: “these things aren’t made to be driven in 4WD on the pavement”.
 

Shark56

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When you have it jacked up. Did you try turning the front wheels by hand with the hubs locked and it in 4x4?
A little play in wheel bearing could be you just did not get tight enough.
I'm guessing you have a floor shift transfer case. Any difference in 4 lo?
4x4 on pavement won't make much of a difference until you do a turn.
 

Skreddy

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If I’m watching this right, that noise is not in the front driveline, axle, wheels, etc. You can see the driveline spinning in the video. The noise is there before the driveline starts spinning which rules out anything from the driveline forward.
Could be the rear bearing on the front output shaft (every t-case I’ve taken apart, thus bearing has been bad). I would lean towards something in the transfer case if this doesn’t do it in 2wd.
Another test to verify: remove front driveshaft and see if the noise still occurs.
 

Goldbug

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If I’m watching this right, that noise is not in the front driveline, axle, wheels, etc. You can see the driveline spinning in the video. The noise is there before the driveline starts spinning which rules out anything from the driveline forward.
Could be the rear bearing on the front output shaft (every t-case I’ve taken apart, thus bearing has been bad). I would lean towards something in the transfer case if this doesn’t do it in 2wd.
Another test to verify: remove front driveshaft and see if the noise still occurs.
Thanks. I’m gonna try removing the front driveshaft and see if it still happens.

I haven’t tried 4Lo, but it only happens at a decent speed, higher than I could go in 4Lo.
 

Goldbug

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I have an idea. Perhaps the noise is because my front drive shaft is not properly aligned/assembled. I put the rear back on and it made a bit of a new noise and I realized that when the yoke slipped out, I put it back in without thinking.

Referencing this old thread: Alignment of driveshaft yokes & mystery vibrations - https://forum.ih8mud.com/threads/alignment-of-driveshaft-yokes-mystery-vibrations.220571/

This is the front currently, doesn’t look like the U joints line up?

image.jpg
 
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Your ujoints are out of phase and that is most likely the source of the noise. I have experienced the same thing and same noise in my early cruiser days before I knew U-joints needed to be phased.
 
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They look out of phase from the pic. Use a long straight edge to check. If out of phase that will cause a vibration especially on lifted trucks.
 

Skreddy

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I believe you need to rephrase and line up the ones I’m indicating in red.
E5A9324D-62C0-475D-8BC3-208B61594A54.jpeg
 

Goldbug

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There are few things in life I find more satisfying than solving a problem with the 40. Just drove it in 2Hi and the new rattle is gone. Drove it in 4 High with hubs locked and unlocked and rattle is gone!

Thanks for the help working this out everyone. Always nice when it’s an easy fix.

Pics of both driveshafts currently, in alignment.



40EC69C6-7F5A-4E4C-BC25-F1B8B0DF629E.jpeg


Front Driveshaft.jpg
 
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Goldbug

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That front still looks out of phase.
How so? I couldn't find any little arrow marks to line up. Is there a better way? I basically tried getting the zerks and U joints to line up as much as possible. Thanks
 

Goldbug

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Whats with the gold washer on the drive line bolts ?
We all need a little bling in our life. Some people just like it less prominent. :rofl:

Honestly, dunno. Was there when I bought it. It's brass I think.
 
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Thats funny, LOL, Brass, soft, good material for washers. I thought the Bilsteins & the U-bolt flip kit was the bling..... Curious , why no flip kit out back ?
 

Goldbug

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Thats funny, LOL, Brass, soft, good material for washers. I thought the Bilsteins & the U-bolt flip kit was the bling..... Curious , why no flip kit out back ?
Ran out of money! Dave makes great stuff, but quality comes at a cost. It's on the list. It's a long list though. Just bought a skid plate, so extra flip kit will wait a little longer.
 

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